[Q] Doesn't recognize the SIM card after upgrading to ICS

Hello guys, i'm new in this forum.

I've recently bought a used Samsung Galaxy Note, factory unlocked. It came with the 2.3.6 version of android and it worked perfectly. But today, i've upgraded it to ICS by KIES (i'm a mac user) and it doesn't recognize my sim card (It says emergency calls only). The phone isn't blocked and it works perfectly, except from that.
I've tried factory resets and everything, and it doesn't work.

Then, i've downgraded it to 2.3.6 again and guest what: IT WORKS!

But then, i upgrade it again to ICS and it doesn't work again. It's not a sim card problem, i've tried another ones and they don't work neither.

Please help me asap, i'm in 2.3.6 now because that's the only way to call in my phone...

Regards from Sevilla, Spain.